• 8 1Я

The range of the in-core Campbelling system is approximately 2 x 10 to 3 x 10 nv

7 11

(see Figure 8-10). This assumes a constant gamma level of 2. 5 x 10 up to 3 x 10 nv, above which the level of the gamma flux increases as the neutron flux increases. The gamma flux reaches 1×10 R/h when the neutron flux is 1 x 10 nv. The lower limit of the operating range with no gamma flux is determined by amplifier noise; the lower limit of the operative range for a hot restart is determined by the gamma flux and amplifier noise. The neutron/gamma output signal ratios can be found from the product of the neutron sensitivity/gamma sensitivity ratio and the ratio of neutron flux to gamma flux.

The upper limit of measurable neutron flux for this system is determined by ion chamber

saturation. The detectprs have passed breakdown tests at 700°F (Figure 4-5). The results of

the in-core counter life test mentioned in Section IV demonstrate that the Campbell chamber has 20 19

a life of at least 10 nvt. At this time the specified life is 10 nvt. Life tests are continuing.

The system is well shielded and filtered to minimize noise susceptibility. Audio-frequency,

radio-frequency, and transient-pulse-conducted and relay-radiated-interference tests have been

conducted (<• 1 percent added to signal due to these sources). The detector is retracted at.


5 x 10 nv to avoid excessive neutron and gamma exposures and a large. temperature rise in a dry tube.